1. Field of the Invention
The present invention relates to a method for preparing a Rhus verniciflua stokes extract having an increased content of an active flavonoid compound by performing a gas bubbling treatment on the Rhus verniciflua stokes extract; the Rhus verniciflua stokes extract prepared by the above method; and a method of converting fustin into fisetin by performing a gas bubbling treatment on a solution containing fustin.
2. Discussion of Related Art
Rhus verniciflua stokes is fallen leaves broad leaf arborescent belonging to the Anacardiaceae family and it is known that Rhus verniciflua stokes is originally from the Himalayas and highlands of Central Asia. It is now distributed widely throughout the world, from the subtropics to the temperate regions, with the tropics as the center. Rhus verniciflua stokes is fallen leaves or evergreen trees and most of them are shrub trees or tall trees, but some of them are climbing trees (Barkley Fred Alexander., Ann. of the Missouri Bot. Garden., 24(3), pp 265-500, 1937).
A sap of Rhus verniciflua stokes is known as an oriental lacquer. In terms of oriental medicine, it is widely known that a dried oriental lacquer removes extravasated blood; improves blood circulation; and is effective in reducing or alleviating hookworm, stomachache, excessive acid in the stomach, thick sputum, tuberculosis, period pains, constipation, diabetes, malaria, anti-inflammatory, arthritis, and is useful for use as a preservative, strengthening the stomach, easing menstruation pain, and the like, and it is recently known that it is effective in preventing cancer (Namba, T., Colored Illustrations of Wakan Yaku. p 215, Hoikusha Publishing Co. Ltd., Osaka, 1980). In addition, in terms of common medicine, it is known that it is useful as a digestive medicine; it controls extravasated blood in the liver; it controls cardiac disease as a drug for cleaning blood in the heart; removes tuberculosis germs in the lung; and also it is an excellent drug for neuralgia, arthritis, skin diseases, and the like because Rhus verniciflua stokes and a wild ginseng are comparable to each other in effect.
It is already known from much research that Rhus verniciflua stokes include a lot of anti-oxidative substances. Specifically, it is known that the Rhus verniciflua stokes extract that is extracted by using ethanol has strong anti-oxidative activity and also the fraction that is isolated and purified by using a silica column has an ability for inhibiting the growth of tumor cells in the human blood. In addition, it is also known that a substance having an antimicrobial effect is isolated from the Rhus verniciflua stokes extract that is extracted by using ethanol and Rhus verniciflua stokes skin extract that is extracted by using methanol has various bioactivity effects related to the Rhus verniciflua stokes extract, such as an effect on suppressing obesity.
Compounds that are found in Rhus verniciflua stokes genus until now include fisetin, fustin, agathisflavone, eicosanedioic acid, europetein, butein, corilagin, 3′4′-dihydroxy-flavone, lantabetulic acid, myricetin, syringin, semialatic acid, palasitrin, sulfuretin, 3-pentadecyl-1,2-benzenediol, demethoxykanugin, ovalitenone, semimornic acid, 2-(3,4-dihydroxybenzyl)-2,6-dihydroxy-3(2H)-benzofuranone, mesuaferrone A, resokaempferol, rhoifolin, rhusflavanone, succedaneaflavanone, fisetin; 7-0-β-D-glucopyranoside, bhilawanol, tannin, hydrolaccol, stellacyanin, quercetin, cynarine, and the like, and the largest content of the components among them is fustin.
The above components are mostly flavonoid-based materials and flavonoids, such as fisetin and fustin, which play a role in protecting blood vessels or capillaries. And also, the fisetin and fustin are very excellent bioactive substances having antioxidative activity, anti-inflammatory properties, and anticancer properties. However, the fustin that is plentifully included in the Rhus verniciflua stokes extract has a disadvantage wherein its activity is greatly decreased as compared to the activity of fisetin in terms of bioactivity. On the other hand, the fisetin has activitystrong anticancer activity so that it is now being used as an anticancer drug, but there is a disadvantage that a major component of most conventional Rhus verniciflua stokes extracts is the fustin and the fisetin is included in small quantity as compared to the fustin.
Accordingly, when the Rhus verniciflua stokes extract containing a lot of fisetin with excellent bioactivity may be prepared, the Rhus verniciflua stokes extract may have relatively excellent anticancer activity and bioactivity so that it can be expected to be very useful in the food and medicine industries.